Best Way To SELECT From Database

Not totally sure if this is the best place for this question, but regarding maintainability / good practice issues vs speed I have a question regarding what is the best way to SELECT some data from a database.I have the item_id of an item bought.  I want to get a customer's billing information based on the item he bought.  Should I do this with two queries or one using joins?

Here is my dbase schema:

customer_info--------------customer_idnamecc_numexpdate

item_bought------------item_idcustomer_id

And here is a basic pseudocode algorithm:function getCustomerInfo(customerID){    SELECT customer_info.name, customer_info.cc_num, customer_info.expdate FROM customer_info WHERE    customer_id=customerID;   return results;}

function getCustomerInfoWithItemId(itemID){   SELECT item_bought.customer_id FROM item_bought WHERE item_bought.item_id=itemID;      results = getCustomerInfo(customer_Id);

   return results;}

results = getCustomerInfoWithItemId(400);OR

function getCustomerInfoWithItemId(itemID){  SELECT customer_info.name, customer_info.cc_num, customer_info.expdate FROM customer_info, item_bought WHERE item_bought.item_id=itemIDAND customer_info.customer_id = item_bought.customer_id;   return results;}

results = getCustomerInfoWithItemId(400);